1. Field
The present disclosure generally relates to additive manufacturing techniques, and deals more particularly with a method and apparatus for deposition of fiber reinforced polymers, such as thermoplastic polymers.
2. Background
Additive manufacturing is a process in which physical parts are produced directly from a 3-D (three dimensional) CAD (computer aided design) file. In one type of additive manufacturing known as fused deposition modeling (FDM®) and sometimes referred to as 3-D printing, a part is produced by extruding small beads of thermoplastic polymer material to form layers of the material that solidifies after being extruded from a nozzle. The extrusion nozzle may be moved along a toolpath or “rastered” by a numerically controlled mechanism to build the part from the bottom up on a build platform, one layer at a time.
Parts produced by known additive manufacturing processes, such as FDM®, may not be suitable for use in some applications requiring high structural performance, such as in the aerospace industry. In order to achieve higher structural performance, thermoplastic parts used in these applications typically require the use of an embedded reinforcement such as discontinuous or continuous fibers. However, the integration of a continuous fiber reinforcement into an extruded thermoplastic polymer during fused deposition modeling has not been heretofore practical.
It is known to introduce discontinuous (e.g. “chopped”) reinforcing fibers into an extruded polymer. For example, a process known as PUSHTRUSION® has been developed for molding reinforced polymer composites using a direct, in-line compounding and molding process, in which the mold charge comprises extruded polymer pellets or strands reinforced with discontinuous fibers. However, the PUSHTRUSION® process utilizes large and heavy industrial equipment meant to provide discontinuous fiber reinforced polymer strands or pellets for molding, and is not suitable for use in additive manufacturing processes such as FDM.
Accordingly, there is a need for an additive manufacturing process such as FDM that allows integration of a reinforcement into a bead of polymer deposited in layers to form features of a part. There is also a need for an end effector to carry out the process described above which allows entrainment of a continuous reinforcement into a liquified polymer as the end effector builds features of the part.